Thai is messed up in message bodies

[John Francis Lee <jfl 28amen org>]

สวัสดีครับ,

I'm having trouble typing Thai into message bodies. The above looks ok 
now... a little on the small side... but when I get it, or you get it, 
the vowels will not be over the consonants as they should be but will 
be in the air next to them.

I had this trouble with Thunderbird and have wasted the past 2 or 3 
days asking for help there... so I downloaded balsa and... I have the 
same problem here!

I havew no trouble tyoing Thai in openoffice or jEdit... well a little 
in jEdit, but nothing like here or in Thunderbird.

Can i just not get ther from here/ Do I have to use yahoo.com mail to 
correspond with my Thai friends?